The present invention relates to a catheter, and more specifically, a catheter which can be continuously or temporarily retained inside a blood vessel or the like of a patient so that medication liquid such as carcinostatic substance can be injected in an appropriate manner.
Conventionally, when medication liquid such as a carcinostatic substance is to be dosed to a patient, the medication liquid is generally injected into a blood vessel of the patient""s body by using a syringe or an instillator. However, in this conventional method, there is a problem that the medication liquid affects not only cancer cells but also normal cells because the liquid is circulated throughout the body through the blood vessels.
Therefore, there has been an attempt to insert a catheter into a blood vessel through the skin and the front end of the catheter is located at the inlet position of the arterial canal extending to an internal organ having cancer, so that the medication liquid is directly injected into the internal organ having the cancer and a significant carcinostatic effect is achieved with a relatively small amount of dose.
In this attempt, after the catheter has been inserted into the patient""s body such that the front end of the catheter is located at the inlet position of the arterial canal extending to the targeted internal organ, the base portion side of the catheter is fixed on the patient""s body so that the front end of the catheter should not move from the determined inlet position during the injection of the medication liquid.
However, in this conventional method, although the base portion side of the catheter is fixed on the patient""s body, the front end portion of the catheter could move from the determined position during the injection due to, for example, movement of patient""s body during sleep, resulting in flow of the medication liquid to some internal organs other than the targeted one.
In order to overcome such problems, Japanese Patent Application, Laid-Open Publication No. 10-272187 proposes a catheter in which a wire material having elasticity and a curved shape is provided at the front end inner peripheral portion of the tube-shaped catheter main body so that the front end portion of the catheter main body has a curved shape and this curve-shaped front end portion of the catheter is pressingly fixed on the wall of the blood vessel.
However, in the case of the catheter disclosed in Japanese Patent Application Laid-Open Publication No. 10-272187, as the wire material is inserted at the front end portion of the catheter main body, the flow of the medication liquid is disturbed at that portion. In addition, it is not possible to put a guide wire through the front end portion for the same reason.
Accordingly, when the catheter disclosed in Japanese Patent Application Laid-Open Publication No. 10-272187 is to be inserted into the blood vessel, the following steps are required: 1) a guide wire is inserted first and its from end is disposed at the targeted position; 2) a parent catheter is inserted along the outer periphery of the guide wire; 3) the guide wire is pulled out when the front end of the patent catheter reaches the targeted position; 4) and the catheter for dosing the medication liquid is inserted through the parent catheter.
As a result, complicated and time-consuming work is required for inserting the catheter for dosing the medication liquid. In addition, there arises another problem, an insertion portion which is larger than the sectional area of the catheter for dosing the medication liquid has to be created on the patient""s body because the parent catheter has a larger diameter than the catheter for dosing the medication liquid.
The present invention solves the aforementioned problems observed in use of the conventional catheter. An object of the present invention is to provide a catheter which can be continuously or temporarily retained in a blood vessel or the like of a patient""s body and which requires only a quick and simple operation for insertion and a relatively small insertion portion.
The catheter of the present invention includes a tube-shaped catheter main body, a shaping member which is provided at least at the front end portion of the catheter main body for imparting a winding shape to the front end portion of the catheter, and a cavity portion formed at the inner side of the shaping member.
Due to the structure described above, a guide wire can be very easily inserted through the cavity portion of the catheter. Specifically, the guide wire is first inserted into a blood vessel or the like of a subject and the front end portion of the guide wire is disposed at the targeted site. The catheter is then inserted along the outer periphery of the guide wire. Accordingly, the catheter can reliably be disposed at the targeted position.
When the catheter is disposed at the targeted site, or more specifically, when the front end portion of the catheter has reached the front end portion of the guide wire, the guide wire is pulled out so that the front end portion of the catheter restores its winding shape.
The catheter can be then retained, in such a state, continuously or temporarily in the patient""s body, so that the medication liquid is reliably dosed to the targeted portion of the subject (the patient""s body) through the catheter retained in such a manner.
Accordingly, the catheter can be inserted directly into the patient""s body without using a parent catheter. As a result, only a simple and quick operation in a relatively small insertion portion is necessitated for insertion of the catheter.
The winding front end portion of the catheter preferably has a spiral structure, such that the front end portion of the catheter can be reliably pressed and fixed on the inner periphery of the blood vessel.
In addition, the shaping member is formed preferably of a super elastic material so that the shaping member easily takes on a linear shape when the guide wire is inserted and restores the winding shape when the guide wire is pulled out.
Specifically, such a elastic material preferably containing at least one of the following alloys including Nixe2x80x94Ti alloy, Cuxe2x80x94Znxe2x80x94X alloy (X=Al or Fe) and Nixe2x80x94Tixe2x80x94X (X=Fe, Cu, V or Co).
In addition, the shaping member is preferably constructed as a coil, so that the cavity portion can be reliably secured and thus the guide wire can be inserted smoothly.
Further, the coil, preferably has a flat portion on the cavity portion side, so that the cavity portion can be more reliably secured and thus the guide wire can be inserted more smoothly.
The shaping member preferably has a double-leave in structure when imparting a winding shape to the front end portion of the catheter main body, so that the cavity portion can be reliably secured.
Alternatively, the shaping member may be structured as a mesh tube.
Further, in the front end of the catheter main body, the peripheral wall of the portion to which a winding shape is imparted by the shaping member is preferably provided with holes so that the medication liquid flows out through the holes. More specifically, the winding shape is a spiral shape and the holes are formed at the inner side of the spiral shape so that the medication liquid is not directly injected onto the blood vessel of the subject.
The winding shape preferably has a diameter which is larger than the diameter of the retention site of the subject, so that the front end portion is reliably retained at the retention site.